For example, JP-2009-006855-A discloses a hydraulic control apparatus which includes a base body and a housing. The housing includes a housing fixing hole formed in the surface thereof facing the base body, and the base body includes a housing mounting penetration hole. The housing is mounted onto the base body by inserting a housing fixing screw into the housing mounting penetration hole of the base body from the back surface to the front surface (housing mounting surface), and by thread-tightening the leading end of the fixing screw with a female screw of the housing fixing hole of the housing.
When electric parts, such as a solenoid coil (electric part assembly) to be mounted on an electromagnetic valve and an ECU, are assembled to the housing, or when a cover is fixed to the housing, the housing will be fixed provisionally. In view of manufacturability, it may be attempted to provisionally fix the housing by inserting a provisionally fixing pin into the housing fixing hole. However, such method is not preferable since the provisionally fixing pin inserted into the housing fixing hole also contacts the female screw formed therein. To avoid the contact between the female screw in the fixing hole and the fixing pin, the housing can be simply gripped as a provisional fixing without using the fixing pin. But, in this case, the gripping part of a sufficient size may be required, resulting in the complicated structure.